The present invention is directed to ink compositions and more specifically, the present invention relates to hot melt inks with for example, a melting point of between about 25.degree. C. and about 40.degree. C., or from about 30 to about 35 degrees Centigrade, and which inks are especially useful for acoustic ink printing, processes and apparatuses, reference, for example, U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, and U.S. Pat. No. 5,371,531, the disclosures of which are totally incorporated herein by reference, including especially acoustic ink processes as illustrated in some of the aforementioned copending applications and patents, such as an acoustic ink printer for printing images on a record medium.
The inks of the present invention in embodiments thereof are comprised of (1) a liquid non-aqueous vehicle, such as a cyclic ketone, with a boiling point of higher than about, or equal to about 150.degree. C. (Centigrade throughout) and lower than about, or equal to about 350.degree. C., and more specifically from about 175 to about 325, and yet more specifically from about 225 to about 300 degrees Centigrade, and with a low acoustic loss which reduces, or minimizes energy consumption, and which acoustic loss is for example, below, or about equal to 60 dB/mm, (2) a solid additive, preferably contained in the imaging substrate, or paper pores and with a melting point of for example, lower than, or equal to about 75.degree. C. and preferably between about 35 to about 74.degree. C. (Centigrade) and with a low acoustic loss, and which acoustic loss is for example, below, or equal to about 100 dB/mm, (3) a light fastness UV absorber, (4) a light fastness antioxidant, (5) and a colorant such as a dye, a pigment or mixtures thereof. More specifically, the present invention is directed to semi-solid hot melt acoustic ink compositions comprised of (1) a liquid ketone vehicles with a boiling point of higher than, or equal to about 150.degree. C. and lower than, or equal to about 350.degree. C., and preferably between about 170 to about 300.degree. C., and with a low acoustic loss to thereby reduce or minimize energy consumption, and which acoustic loss is below or equal to about 60 dB/mm, and preferably is in the range of between about 5 to about 40 dB/mm, (2) a solid compound, preferably a ketone, with a melting point of for example, lower than, or equal to about 75.degree. C. and preferably between about 35 and about 74.degree. C., with low acoustic loss to reduce, or minimize energy consumption, and which acoustic loss is below, or about equal to 100 dB/mm, and preferably in the range of from about 25 to about 80 dB/mm, (3) a UV absorber, (4) an antioxidant, and (5) a colorant, and wherein there can be generated with such inks excellent developed images on plain and coated papers with acceptable image permanence, excellent projection efficiency on transparencies without a post fusing step, and excellent crease resistance, and wherein the inks possess acceptable, and in embodiments superior lightfastness, and superior waterfastness. Moreover, in embodiments of the present invention there is enabled the elimination, or minimization of undesirable paper curl since water need not be present in the invention inks, and it is preferred that there be an absence of water, and when water is not present in the inks a dryer can be avoided thereby minimizing the cost of the acoustic ink jet apparatus and processes.